Precise Dosing of Pramipexole for Low-Dosed Filament Production by Hot Melt Extrusion Applying Various Feeding Methods.

The aim of this research was the production of low-dosed filaments via hot-melt extrusion (HME) with the model drug pramipexole for the treatment of Parkinson's disease. The active pharmaceutical ingredient (API) and one of the polymers polyvinyl alcohol (PVA) or basic butylated methacrylate copolymer (bPMMA) were fed by various dosing techniques with the aim of achieving the smallest deviation (RSD) from the target concentration of 0.1% (w/w) pramipexole. It was found that deviation from target pramipexole concentration occurred due to degradation products in bPMMA formulations. Additionally, material temperature above 120 °C led to the formation of the anhydrous form of pramipexole within the extruded filaments and need to be considered in the calculation of the recovered API. This study clearly shows that even if equilibrium state of the extrusion parameters was reached, equilibrium condition for drug content was reached relatively late in the process. In addition, the RSD calculated by the Stange-Poole equation was proposed by us to predict the final content uniformity considering the sample size of the analyzed filament. The calculated RSD, depending on sample size and drug load, can serve as upper and lower limits of variation from target concentration and can be used to evaluate the deviations of drug content in equilibrium conditions of the HME process. The lowest deviations from target concentration in equilibrium condition for drug content were obtained in filaments extruded from previously prepared granule mixtures (RSD = 6.00%, acceptance value = 12.2). These promising results can be transferred to other API-excipient combinations to produce low-dosed filaments, which can be used for, e.g., fused filament 3D printing. The introduced calculation of the RSD by Stange-Poole equation can be used for precise determination of the homogeneity of an extruded batch.

Quality of FDM 3D Printed Medicines for Pediatrics: Considerations for Formulation Development, Filament Extrusion, Printing Process and Printer Design.

3d printing is capable of providing dose individualization for pediatric medicines and translating the precision medicine approach into practical application. In pediatrics, dose individualization and preparation of small dosage forms is a requirement for successful therapy, which is frequently not possible due to the lack of suitable dosage forms. For precision medicine, individual characteristics of patients are considered for the selection of the best possible API in the most suitable dose with the most effective release profile to improve therapeutic outcome. 3d printing is inherently suitable for manufacturing of individualized medicines with varying dosages, sizes, release profiles and drug combinations in small batch sizes, which cannot be manufactured with traditional technologies. However, understanding of critical quality attributes and process parameters still needs to be significantly improved for this new technology. To ensure health and safety of patients, cleaning and process validation needs to be established. Additionally, adequate analytical methods for the in-process control of intermediates, regarding their printability as well as control of the final 3d printed tablets considering any risk of this new technology will be required. The PolyPrint consortium is actively working on developing novel polymers for fused deposition modeling (FDM) 3d printing, filament formulation and manufacturing development as well as optimization of the printing process, and the design of a GMP-capable FDM 3d printer. In this manuscript, the consortium shares its views on quality aspects and measures for 3d printing from drug-loaded filaments, including formulation development, the printing process, and the printed dosage forms. Additionally, engineering approaches for quality assurance during the printing process and for the final dosage form will be presented together with considerations for a GMP-capable printer design.

Targeting the Central Nervous System (CNS): A Review of Rabies Virus-Targeting Strategies.

The transport of drugs across the blood-brain barrier is challenging. The use of peptide sequences derived from viruses with a central nervous system (CNS) tropism is one elegant option. A prominent example is the rabies virus glycopeptide-29 (RVG-29), which is said to enable a targeted brain delivery. Although the entry mechanism of the rabies virus into the CNS is very well characterized, it is unknown whether RVG-29-functionalized drug delivery systems (DDSs) follow this pathway. RVG-29-functionalized DDSs present themselves with modifications of the RVG-29 peptide sequence and different physicochemical properties compared to the rabies virus. To our surprise, the impact of these changes on the functionality is completely neglected. This review explores virus-related CNS-targeting strategies by comparing RVG-29-functionalized DDSs with regard to their peptide modification, physiochemical properties and their behavior in cell culture studies with a special focus on the original pathway of rabies virus entry into the CNS.

Determination of the activity of maleimide-functionalized phospholipids during preparation of liposomes.

Numerous examples exist in the literature for the use of maleimide-thiol-reactions in the area of functionalized nanoparticles. Although the hydrolysis tendency of maleimides is well-known, qualitative and quantitative information on the stability and reactivity of maleimide groups during preparation and in final formulations are missing. This is surprising, since hydrolysis of maleimides prevents nanoparticle functionalization and results in an increase of negative surface charge due to the hydrolysis product maleic acid. In this study we investigated the stability of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[maleimide-2000] (DSPE-PEG2000-Mal) during the preparation of liposomes via two common preparation methods, which can be distinguished by the insertion of DSPE-PEG2000-Mal during or after the liposome formation process (pre-insertion and post-insertion process). The liposomes prepared by the pre-insertion method had 63% active maleimide groups remaining on their surface. The activity decreased dramatically during the purification process down to 32%. The preparation by post-insertion showed minimal effects with regard to maleimide activity. 76% of maleimide groups were active and therefore available for coupling reaction. By identifying active maleimide groups on the surface of the final formulations, the presented work revealed the dramatic impact of preparation methods on the activity of maleimide groups.

HPLC analysis as a tool for assessing targeted liposome composition.

Functionalized phospholipids are indispensable materials for the design of targeted liposomes. Control over the quality and quantity of phospholipids is thereby key in the successful development and manufacture of such formulations. This was also the case for a complex liposomal preparation composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), Cholesterol (CHO), 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethylene glycol)-2000] (DSPE-PEG2000). To this end, an RP-HPLC method was developed. Detection was done via evaporative light scattering (ELS) for liposomal components. The method was validated for linearity, precision, accuracy, sensitivity and robustness. The liposomal compounds had a non-linear quadratic response in the concentration range of 0.012-0.42 mg/ml with a correlation coefficient greater than 0.99 with an accuracy of method confirmed 95-105% of the theoretical concentration. Furthermore, degradation products from the liposomal formulation could be identified. The presented method was successfully implemented as a control tool during the preparation of functionalized liposomes. It underlined the benefit of HPLC analysis of phospholipids during liposome preparation as an easy and rapid control method for the functionalized lipid at each preparation step as well as for the quantification of all components.

Premature drug release of polymeric micelles and its effects on tumor targeting.

Based on the enhanced permeability and retention (EPR) effect, nanoparticles are believed to accumulate in tumors. In this conjunction, the stability of drug encapsulation is assumed to be sufficient. For clarification purposes, PEGylated poly-(D,L-lactic acid) (PEG-PDLLA) micelles which incorporated the hydrophobic model drug dechloro-4-iodo-fenofibrate (IFF) were investigated. H2N-PEG-PDLLA was synthesized, coupled to 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) and labeled with 111-indium. From this polymeric species, mixed micelles with H3CO-PEG-PDLLA were prepared which encapsulated the 125-iodine or 131-iodine labeled drug IFF. Bioimaging and biodistribution experiments in healthy and AR42J-tumor bearing mice were carried out to quantify the uptake of the drug and its carrier in single organs. As a result, upon injection of this system, a rapid dissociation of the polymeric carrier and the incorporated drug (<10 min post inj.) was revealed. Regardless of the premature release, the drug showed an enhanced tumor accumulation compared to the polymeric carrier. In conclusion, the self-assembling system allowed for successful solubilization of the hydrophobic drug by physical incorporation into micelles whereas the tumor targeting properties of the drug delivery system could not be sufficiently shown.

Development of a new method to assess nanocrystal dissolution based on light scattering.

PURPOSE: Nanocrystals exhibit enhanced dissolution rates and can effectively increase the bioavailability of poorly water soluble drug substances. However, methods for in vitro characterization of dissolution are unavailable. The objective of this study was to develop an in situ noninvasive analytical method to measure dissolution of crystalline nanosuspensions based on light scattering. METHODS: Fenofibrate nanosuspensions were prepared by wet media milling. Their solubilities and dissolution profiles in simulated gastric fluid supplemented with 0.1% Tween(®) 80 were measured in a small scale setup with an instrument for dynamic light scattering and the intensity of scattered light as readout parameter. RESULTS: A good correlation was achieved between the dissolution profile of a nanosuspension measured in the light scattering setup and a conventional dissolution experiment. Nanosuspensions of 120-270 nm size could be distinguished by the light scattering method. The suspensions dissolved within 1.9-12.3 min. Over a concentration range of 40-87% of the solubility dissolution profiles of a nanosuspension with 140 nm were monitored and the determined total dissolution times were in good agreement with the Noyes-Whitney dissolution model. CONCLUSIONS: A noninvasive, sensitive and reproducible method is presented to assess nanocrystal dissolution. In situ measurements based on light scattering allow a straightforward experimental setup with high temporal resolution.

Radioiodinated dechloro-4-iodofenofibrate: a hydrophobic model drug for molecular imaging studies.

Radiolabeling is a valuable option for tracking drug molecules in biodistribution experiments. In the development of innovative drug delivery systems the influence of the pharmaceutical formulation on the drugs' pharmacokinetics has to be investigated. The hypolipidemic agent fenofibrate is an ideal model drug for testing the performance of drug delivery systems designed for poorly soluble compounds. Herein, we report a de novo synthesis of a fenofibrate derivative, dechloro-4-iodofenofibrate, as well as its conversion into its radioiodinated derivatives containing (125)I or (131)I. The enzymatic stability of the radiolabeled compounds synthesized was determined in vitro. A scintigraphic imaging study supplemented by biodistribution experiments and analysis of excreted metabolites revealed the stability required for in vivo applications and its similarity to fenofibrate. Therefore a convenient method is presented to synthesize radioiodinated derivatives of fenofibrate. These tracers show excellent in vitro and in vivo properties to study the behavior of lipophilic drugs.

Controlled delivery of nanosuspensions from osmotic pumps: zero order and non-zero order kinetics.

Nanosuspensions have gained great interest in the last decade as a formulation tool for poorly soluble drugs. By decreasing particle sizes nanosuspensions enhance dissolution rate and bioavailability of the active pharmaceutical ingredient. Micro-osmotic pumps are widely used in experimental pharmacology and offer a tool of interest for the sustained release of nanosuspensions via the intraperitoneal or subcutaneous application site. The purpose of the present study was to investigate in-vitro the influence of (1) nanosuspension viscosity, (2) pump orifice position and (3) formulation osmolality on the delivery behavior of formulations in implantable osmotic systems. Therefore fenofibrate nanosuspension, methylene blue and fluorescein sodium solutions were chosen as model formulations. They were released in water or isotonic saline solution and drug/dye concentrations were determined by HPLC/UV. Release of nanosuspension particles in low viscous formulations resulted in a burst whereas increasing the viscosity led to the expected zero order delivery. Pumps with upward-positioned orifices released the nanosuspension in a zero order manner. Within the release of dyes, constant delivery could be ensured up to an osmolality of 486 mO sm/kg; above this value premature release of formulation was observed. The results indicate the requirement of in-vitro experiments prior to in-vivo animal testing for determining the release profiles of osmotic pumps.